Swap Opal Incandescent Bulb with LED Bulb?

Yesterday I swapped out a broken LPL 6700 enlarger with a simple two condenser lens (similar to Leitz focamat type, Mars 66 made in Japan brand) enlarger in the darkroom where I teach. It was brand new in the box, and was the only complete enlarger setup in storage, so better a older working enlarger than a empty enlarger station. It fires up and works fine, but the lamp house heats up quickly and gets quite hot especially with extended focusing times. Since I teach a number of kids in this darkroom routinely, I thought a cooler LED solution would be safer.

Has anyone swapped out the typical opal enlarger bulb with an LED type? I am curious if the little LED bulbs that are clustered to make the entire bulb, gives off light that is not even enough for enlarging. I have seen a few LED bulbs in stores, but I can clearly see the smaller LEDs under the diffusing cover clearly when lit up. Because this is a condenser type do you think there is a chance that this would affect the output when printing?

Also should I look for a warmer or cooler color temp bulb? We use variable contrast papers mainly.

Check the bulb rating of the enlarger.
Some will take 150w bulbs, others max at 75w.
If it is getting HOT, and you have short exposure times, I think you have a bulb that is too big for the enlarger. Drop down to a lower wattage bulb, and it will run cooler.
My Durst M600 is rated for a 150w bulb, but I use a 75w bulb in it, and sometimes I which I could find a 40w photo bulb.

Well the setup doesn't get super hot right away, but I think if left on for a more extended time, such as when a new student first uses a grain magnifier or if they are trying to figure out how best to place the image on the easel, or test different magnification of the image, or practicing dodging and burning certain areas, the enlarger can potentially get hot to the touch. A 40w opal photo bulb would probably work pretty well. Right now a 150w bulb is installed as it was the last photobulb size in the darkroom, all the rest are the double pin type bulbs. I have not had any students use it yet as I installed it at the end of the day.

I agree with the comment about LED bulbs, the claim is that they do as good a job as traditional bulbs, but my experience (not with enlargers) is that they aren't as bright and the light is a lot harsher to the eye.

I use a pair of Omega D2s and they have 75 watts bulbs. When I had an 150 watts in there, it got EXTREMELY HOT and they were too bright. With 75 watts, extended focusing doesn't give me any issues. It does get warm but not overly or dangerously so. That may a cheaper and better alternative. I can print both 35mm and medium format for reasonable size with no issues.

A properly designed condenser enlarger has light-baffled air vents at the bottom and top of the lamp house. As air inside the housing heats, it rises upward and out of the upper exhaust vents. That rising air flowing out of the upper exhaust vents causes cooler ambient air to be drawn in through the lower air intake vents. This air flow limits the temperature inside the housing to a safe level.

For example, I have a Beseler 23C II enlarger equipped with the 75-watt PH-111 opal photo lamp. When the lamp is left on continuously for several minutes the housing gets warm, but not excessively so. The heated air flow rising out of the vents is noticeable by placing my hands above the vents. Even after several minutes of continuous operation the surface of the housing is warm to the touch, but not dangerously so. The cooling system is adequate to keep the lamp house at a safe temperature.

The maximum temperature inside the housing is proportional to the current rating of the bulb. It would be prudent to check the following (some of which have already been cited in previous posts):

1. The current rating of the bulb. This type and size of enlarger (probably 6 x 6cm given the name “Mars 66”) is most likely intended for a 75-watt opal photo lamp. If the lamp installed is of a higher current rating, changing the bulb will lower the operating temperature of the enlarger.

2. Verify that the air vents are not covered with something, such as packing material.

3. If it still runs too hot, you can install a variable bulb dimmer intended for conventional incandescent bulbs in the AC line. With this, you could reduce the current to the lamp to limit the heat to a tolerable level. Here’s an example that could be installed into a simple box housing and is inexpensive.

Swap Opal Incandescent Bulb with LED Bulb?

Ah thanks for the suggestions. I suspected the 75w lamp would have been the right size. The enlarger did not have a manual and only a promotional ad pamphlet with only 1 picture on it. I did not remember seeing vents but I could be wrong, I'll double check.

You are correct it is a 6x6 enlarger, it comes with a 6x6 carrier as well as a 75mm lens preinstalled. It also came with a 35mm neg carrier and 50mm lens. I forgot the brand of lens but they were 25mm thread.

I will pick up a 75w bulb, b&h has them online for less than $5, maybe they have them in store too.

If I get a chance I would like to try out the CFL and LED options and test it, but I have a feeling that those bulbs are just not frosted/opal covered enough to eliminate hot spots in a condenser setup. As well as the potential difficulties with using vc papers. I really thought someone atleast had tried this with one of their enlargers.

Yes, but not as simply as swapping the bulb. There was someone posting both here and on LFPF and making very nice replacement Omega D lamphouses using careful color matched LEDs. I bought one and love it. Evennness is at least equal to what I get with a 211 or 212, VC response to filters seems the same, there is virtually no heat and no worries about negative popping and the lamp life is rated at something like 30k or 35k hours. Brightness is just about evenly in between a 75W 211 and a 150W 212, which is fine for my work. See the thread here: